Secondary battery

ABSTRACT

A secondary battery capable of being formed to be relatively small by reducing the sizes of internal devices and compactly locating the internal devices. Accordingly, the volume of the secondary battery is reduced and the capacity thereof is maintained, thereby increasing the capacity density of the secondary battery. In one embodiment, the secondary battery includes a bare cell having a cap plate and a protection circuit module on the bare cell and including a printed circuit board surface-contacting the cap plate.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/397,578, filed Mar. 4, 2009, which claims priority to and the benefitof U.S. Provisional Patent Application No. 61/099,138, filed on Sep. 22,2008, the entire content of both of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a secondary battery.

2. Description of the Related Art

A lithium ion secondary battery includes a core pack having a bare celland a protection circuit module.

The bare cell includes a positive electrode plate, a negative electrodeplate, and a separator, supplies electric power to external electronicdevices, and is capable of being repeatedly charged and discharged. Theprotection circuit module protects the secondary battery from overchargeand overcurrent, and from lowering of performance due to overdischarge.

BRIEF SUMMARY OF THE INVENTION

An aspect of an embodiment of the present invention is directed toward asecondary battery capable of reducing the overall size of the secondarybattery, and/or increasing the power density (or capacity density) ofthe secondary battery.

An embodiment of the present invention provides a secondary batteryincluding a bare cell and a protection circuit module. The bare cellincludes a cap plate, and the protection circuit module is on the barecell and includes a printed circuit board surface-contacting the capplate.

In one embodiment, the printed circuit board is a flexible printedcircuit board. The flexible printed circuit board includes an insulatingportion on a surface thereof facing the cap plate.

In one embodiment, the protection circuit module includes acharge/discharge terminal section on the printed circuit board and forelectrically connecting the bare cell to an external device. Thecharge/discharge terminal section may include a housing and acharge/discharge terminal on the housing, and the charge/dischargeterminal section may be surface mounted to the printed circuit board. Inaddition, the charge/discharge terminal of the charge/discharge terminalsection may be surface mounted on a side of the printed circuit boardfacing away from the bare cell. The housing may be composed of aninsulation material, and the charge/discharge terminal may be composedof a plurality of metal plates. The plurality of metal plates mayinclude a positive electrode, an identification resistor and a negativeelectrode insulated from each other by the housing. The charge/dischargeterminal section may include a base having a flat plate-like shape, afirst support surface mounted on the printed circuit board and forsupporting a first side portion of the base to be spaced apart from theprinted circuit board, and a second support surface mounted on theprinted circuit board and for supporting a second side portion of thebase to be spaced apart from the printed circuit board. The secondarybattery may further include a protection circuit device on the printedcircuit board and between the first support and the second support,wherein a side of the base facing the protection circuit device may besupported by the first and second supports to be spaced apart from theprotection circuit device.

In one embodiment, the printed circuit board has a thickness betweenabout 0.10 to about 0.15 mm.

In one embodiment, the printed circuit board has smaller area than thatof the cap plate.

In one embodiment, the printed circuit board is mounted on the bare cellwithout any empty space between the printed circuit board and the barecell.

In one embodiment, the secondary battery further includes a positivetemperature coefficient (PTC) section on the printed circuit board.Here, the printed circuit board has a terminal hole, and the bare cellincludes an electrode terminal electrically connected with the PTCsection through the terminal hole. The electrode terminal may extendinto a first end of the terminal hole facing the bare cell and out froma second end of the terminal hole facing away from the bare cell. ThePTC section may include a first tap electrically connected with aterminal on a side of the flexible printed circuit board facing awayfrom the bare cell, a second tap electrically connected with the barecell, and a PTC device electrically connected with the first tap and thesecond tap. The PTC section may be at least a portion of a positive ornegative lead plate.

In one embodiment, the secondary battery may further include a leadplate at a short edge portion of the printed circuit board, the leadplate being electrically and mechanically connected with both the barecell and the printed circuit board.

In one embodiment, the lead plate includes: a first plate having aportion on a top surface of the printed circuit board, and mechanicallyand electrically connected with the printed circuit board at the shortedge portion of the printed circuit board; and a second plate having aportion on a top surface of the bare cell, and mechanically andelectrically connected with the bare cell, the first plate and thesecond plate being electrically connected with each other. In oneembodiment, the lead plate includes: a first plate on and mechanicallyand electrically connected with the printed circuit board at the shortedge portion of the printed circuit board; a second plate on andmechanically and electrically connected with the bare cell; and a thirdplate electrically connecting the first plate and the second plate andhaving a height separating the first plate from the second plate, andwherein the printed circuit board may have a thickness substantiallyidentical to a sum of the height separating the first plate from thesecond plate and a thickness of the second plate. In one embodiment, thelead plate is a substantially flat plate. In addition, the secondarybattery may further include a dummy plate at another short edge portionof the printed circuit board for mechanically connecting the bare cellwith the protection circuit module. Alternatively, the secondary batterymay further include another lead plate at another short edge portion ofthe printed circuit board and electrically connected with the bare cell,the two lead plates being integrated as at least a portion of a positiveor negative lead plate.

In one embodiment, the secondary battery may further include: a label;an upper case at an upper end of the label; and a lower case at a lowerend of the label; the protection circuit module and the bare cell beingwithin the label, the upper case, and the lower case, and the protectioncircuit module being between the upper case and the bare cell.

In one embodiment, the secondary battery may further include: a positivetemperature coefficient (PTC) section on the printed circuit board, thePTC section being at least a portion of a first lead plate having afirst polarity; a lead plate at a short edge portion of the printedcircuit board and electrically connected with the bare cell, the leadplate being at least a portion of a second lead plate having a secondpolarity; and a protection circuit device on the printed circuit boardand between the charge/discharge terminal section and the printedcircuit board.

Another embodiment of the present invention provides a secondary batteryincluding a bare cell and a protection circuit module. The protectioncircuit module is on the bare cell and includes a lead plate at a shortedge portion of the protection circuit module. The lead plate is on atop surface of the bare cell for clamping the protection circuit moduleto the bare cell.

In one embodiment, the protection circuit module is mounted by the leadplate on the bare cell without any empty space between the protectioncircuit module and the bare cell.

Another embodiment of the present invention provides a method of forminga secondary battery. The method includes: forming a protection circuitmodule on a bare cell from a printed circuit board having a first sidecontacting the bare cell without any empty space therebetween; andsurface mounting a charge/discharge terminal section on a second side ofthe printed circuit board for electrically connecting the bare cell toan external device.

In view of the above, the overall size of the secondary batteryaccording to an embodiment of the present invention can be reduced byreducing sizes of the internal devices of the secondary battery andcompactly locating these internal devices in the secondary battery.Accordingly, the overall size (or volume) of the secondary battery isreduced and the capacity thereof is maintained, thereby increasing thecapacity density of the secondary battery.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, together with the specification, illustrateexemplary embodiments of the present invention, and, together with thedescription, serve to explain the principles of the present invention.

FIG. 1 is a schematic exploded perspective view of a secondary batteryaccording to an embodiment of the present invention.

FIG. 2 is a schematic exploded perspective view of a bare cell accordingto an embodiment of the present invention.

FIG. 3 is a schematic exploded perspective view of a protection circuitmodule according to an embodiment of the present invention.

FIG. 4 is a schematic side view of a first lead plate according to anembodiment of the present invention.

FIG. 5 is a schematic sectional view of the secondary battery of FIG. 1according to an embodiment of the present invention.

FIG. 6 is a schematic exploded perspective view of a charge/dischargeterminal section according to an embodiment of the present invention.

FIG. 7 is a schematic perspective view of the charge/discharge terminalsection of FIG. 6 according to an embodiment of the present invention.

FIG. 8 is a schematic perspective view of the secondary battery of FIG.1 according to an embodiment of the present invention.

FIG. 9 is a schematic side view of a first lead plate according toanother embodiment of the present invention.

FIG. 10 is a schematic side view of a first lead plate according to yetanother embodiment of the present invention.

DETAILED DESCRIPTION

In the following detailed description, only certain exemplaryembodiments of the present invention are shown and described, by way ofillustration. As those skilled in the art would recognize, the inventionmay be embodied in many different forms and should not be construed asbeing limited to the embodiments set forth herein. Also, in the contextof the present application, when an element is referred to as being “on”another element, it can be directly on the another element or beindirectly on the another element with one or more intervening elementsinterposed therebetween. Like reference numerals designate like elementsthroughout the specification.

Hereinafter, a secondary battery according to an embodiment of thepresent invention will be described in more detail with reference to theaccompanying drawings.

FIG. 1 is a schematic exploded perspective view of a secondary battery10 according to an embodiment of the present invention.

Referring to FIG. 1, the secondary battery 10 includes a bare cell 100,a protection circuit module 200, an upper case 620, a lower case 640,and a label 660. The protection circuit module 200 is located on thebare cell 100 and is electrically and mechanically connected to the barecell 100. The upper case 620 surrounds portions of the upper end of theprotection circuit module 200 and the upper end of the bare cell 100,and the lower case 640 covers the lower end of the bare cell 100. Theouter surface of the bare cell 100 is surrounded by the label 660 to beprotected thereby.

FIG. 2 is a schematic exploded perspective view of the bare cell 100according to an embodiment of the present invention. FIG. 3 is aschematic exploded perspective view of the protection circuit module 200according to an embodiment of the present invention. FIG. 4 is aschematic side view of a first lead plate 250 according to an embodimentof the present invention. FIG. 5 is a schematic sectional view of thesecondary battery 100 according to an embodiment of the presentinvention.

Referring to FIG. 2 together with FIG. 1, the bare cell 100 includes acan 110, an electrode assembly 120 accommodated inside the can 110, anda cap assembly 130 covering an opening 110 a of the can 110.

The can 110 has a substantially parallelepipedal shape (or prismaticshape), and has an opening 110 a on one side thereof. The can 110 ismade of a metal, and can be utilized as an electrode terminal by itself.

The electrode assembly 120 is inserted into the can 110 through theopening 110 a of the can 110. The electrode assembly 120 is a jelly-rolltype electrode assembly, and includes a first electrode plate 121, asecond electrode plate 122, and a separator 123 located between thefirst electrode plate 121 and the second electrode plate 122. The firstelectrode plate 121, the second electrode plate 122, and the separator123 are wound into a jelly-roll shape (i.e., are wound to form theelectrode assembly 120 having the jelly-roll shape). The electrodeassembly 120 can be utilized to repeatedly store and supply electricpower when the secondary battery 10 is repeatedly charged anddischarged. The first electrode plate 121 includes a first electrodecurrent collector and a first electrode coating portion.

When the first electrode plate 121 is a positive electrode, the firstelectrode current collector is formed of aluminum (Al) foil having highconductivity.

The first electrode coating portion is located on the first electrodecurrent collector, and includes a first electrode active material, aconductive material, and a binder. In this case, the first electrodeactive material is composed of lithium cobalt oxide (LiCoO₂), lithiummanganese oxide (LiMn₂O₄), and/or lithium nickel oxide (LiNiO₂). Carbonblack is used as the conductive material. The binder is obtained bydissolving and dispersing PVDF, SBR, and/or PTFE using a volatilesolvent such as NMP, an organic solvent, or water.

The first electrode current collector includes first electrodenon-coating portions each having no first electrode coating portion atboth side ends of the first electrode collector. A first electrode tab121 a is attached to the first electrode non-coating portion andprotrudes toward the opening 110 a of the can 110. The first electrodetab 121 a is made of aluminum. A first insulation tape is formed at aportion of the first electrode tab 121 a where the first electrode tab121 a is extended out from the electrode assembly 120 to protect thefirst electrode tab 121 a from having a short-circuit with portionsother than the cap plate 131.

The second electrode plate 122 includes a second electrode currentcollector and a second electrode coating portion.

When the second electrode plate 122 is a negative electrode, the secondelectrode current collector is formed of copper (Cu) foil having highconductivity.

The second electrode coating portion is located on the second electrodecurrent collector, and includes a second electrode active material, aconductive material, and a binder. In this case, the second electrodeactive material is composed of a carbon-based material, Si, Sn, tinoxide, composite tin alloys, a transition metal oxide, a lithium metalnitride, and/or a lithium metal oxide. Carbon black is used as theconductive material. The binder is obtained by dissolving and dispersingPVDF, SBR, or PTFE using a volatile solvent such as NMP, an organicsolvent, and/or water. Due to the high conductivity of the secondelectrode active material itself, the second electrode plate 122 may notneed to use an additional conductive material.

The second electrode current collector includes second electrodenon-coating portions each having no second electrode coating portion atboth side ends of the second electrode current collector. A secondelectrode tab 122 a is attached to the second electrode non-coatingportion and protrudes toward the upper opening 110 a of the can 110. Thesecond electrode tab 122 a is made of copper (Cu) and/or nickel (Ni). Asecond insulation tape is formed at a portion of the second electrodetab 122 a where the second electrode tab 122 a is extended out from theelectrode assembly 120 to protect the second electrode tab 121 fromhaving a short-circuit with portions other than the electrode terminal134.

In the embodiment of the present invention, the first electrode plate121 is a positive electrode plate and the second electrode plate 122 isa negative electrode plate, but the first electrode plate 121 may be anegative electrode and the second electrode plate 122 may be a positiveelectrode.

In the prismatic type secondary battery 10 according to an embodiment,the can 110 is or is a part of a positive electrode for performing thefunction of a positive electrode terminal. In this case, when the firstelectrode 121 is a positive electrode plate, the outermost electrodeplate of the jelly-roll electrode assembly 120 may be the firstelectrode plate 121, i.e. the positive electrode plate. On the otherhand, when the first electrode plate 121 is a negative electrode plate,the outermost electrode plate of the jelly-roll electrode assembly 120may be the second electrode plate 122, i.e. the positive electrode plateso that the can 110 can still be the positive electrode.

Hereinafter, an embodiment of the present invention will be described inmore detail on the assumption that the first electrode plate 121 is apositive electrode plate, and the second electrode plate 122 is anegative electrode plate.

The separator 123 is located between the first electrode plate 121 andthe second electrode plate 122. The separator 123 is formed ofpolyethylene (PE), polypropylene (PP), or a porous membrane usingcomposite films of PE and PP. In the electrode assembly 120, theseparator 123 interrupts conduction of electrons between the firstelectrode plate 121 and the second electrode plate 122 and allowslithium ions to move smoothly therethrough. The separator 123 blocks thefirst electrode plate 121 and the second electrode plate 122 from makingcontact with each other and reduces the temperature of the secondarybattery 10 from rising further through shut-down thereof when it risesdue to an external short circuit. In one embodiment, a ceramic layerobtained by mixing a ceramic material with a binder is also formed withthe separator 123 to further protect the first electrode plate 121 fromhaving a short circuit with the second electrode plate 122.

During charge of the secondary battery 10, in the electrode assembly120, lithium ions are intercalated from the first electrode plate 121 tothe second electrode plate 122 such that electric power can be suppliedto the secondary battery 10. On the other hand, during discharge of thesecondary battery 10, lithium ions are deintercalated from the secondelectrode plate 122 to the first electrode plate 121 to supply electricpower to an external electronic device.

The cap assembly 130 includes a cap plate 131, an insulation plate 132,a terminal plate 133, an electrode terminal 134, and a gasket 135. Thecap assembly 130 is coupled to the electrode assembly 120 at the opening110 a of the can 110 to seal the can 110 together with a separateinsulation case 136 located at a lower portion of the cap assembly 130.In addition, an electrolyte injection hole is formed in the insulationcase 136 to inject electrolyte into the electrode assembly 120.

The cap plate 131 is located on the opening 110 a of the can 110, and isformed of a metal plate having a size corresponding to that of theopening 110 a of the can 110. A first hole 131 a of a set (orpredetermined) size is formed at the center of the cap plate 131. Theelectrolyte injection hole is formed on one side of the cap plate 131.The electrolyte is injected into the can 110 through the electrolyteinjection hole, and is sealed by a cover such as a ball. A safety vent131 d is formed at a portion of the cap plate 131 that corresponds inposition to the electrolyte injection hole and at a proximity away fromthe first hole 131 a. A recess is formed into one surface of the capplate 131 such that the safety vent 131 d is placed within the recessand is stepped away from the one surface of the cap plate 131. Whenhigh-pressure gas is generated in the bare cell 100, the safety vent 131is broken to discharge the gas to the outside. The cap plate 131 makescontact with the first electrode tab 121 a to be electrically connectedthereto. Accordingly, the cap plate 131 has the same polarity as that ofthe first electrode plate 121.

The insulation plate 132 has a flat shape and is located at a lowerportion of the cap plate 131. The insulation plate 132 has a second hole132 a at a position corresponding to the first hole 131 a. Theinsulation plate 132 is made of the same (or substantially the same)insulation material as that of the gasket 135.

The terminal plate 133 has a flat shape and is located at a lowerportion of the insulation plate 132. The terminal plate 133 has a thirdhole 133 a at a position corresponding to the second hole 132 a. Theterminal plate 133 is made of nickel or a nickel alloy.

The electrode terminal 134 is inserted into the cap plate 131, theinsulation plate 132, and the terminal plate 133 through the first hole131 a, the second hole 132 a, and the third hole 133 a. The electrodeterminal 134 makes contact with the second electrode tab 122 a to beelectrically connected thereto. Accordingly, the electrode terminal 134has the same polarity as that of the second electrode plate 122.

The gasket 135 is located between the electrode terminal 134 and the capplate 131. The gasket 135 insulates the electrode terminal 134 and thecap plate 131.

The protection circuit module 200 is located on the upper surface of thebare cell 100. The protection circuit module 200 protects the secondarybattery 10 from overcharge and overcurrent and reduces the lowering ofthe performance of the battery due to overdischarge.

Hereinafter, the connection structure between the protection circuitmodule 200 and the bare cell 100 will be described in more detail withreference to FIGS. 3 to 5.

Referring to FIGS. 3 to FIG. 5, the protection circuit module 200according to an embodiment of the present invention includes a printedcircuit board 210, a positive temperature coefficient (PTC) section 220,a protection circuit device 230, a charge/discharge terminal section240, a first lead plate 250, and a second lead plate 260. The printedcircuit board 210 has a size corresponding to that of the cap plate 131(e.g., has a size that is smaller than that of the cap plate 131) andhas a rectangular shape. In addition, in one embodiment, the sideportions of the cap plate 131 have a curvature. A terminal hole 210 a isformed into a position of the printed circuit board 210 that correspondsin position to the electrode terminal 134 of the bare cell 100. Theelectrode terminal 134 and the gasket 135 are inserted into the terminalhole 210 a, and the lower surface of the printed circuit board 210 islocated such that it makes contact with the upper surface of the barecell 100, in particular, the upper surface of the cap plate 131.

In an existing secondary battery, there are some spaces between theprotection circuit module and the bare cell. The some spaces can be atleast the space of (or distance which) a part of the electrode terminalis located on the surface of the cap plate. However, in view of theabove, in the protection circuit module 200 according to an embodimentof the present invention, the printed circuit board 210 makessurface-contact with the upper surface of the bare cell 100. As such,the space between the protection circuit module 200 and the bare cell100 can be removed, thereby making it possible to manufacture a morecompact secondary battery 10. Accordingly, the secondary battery 10 canbe made smaller or miniaturized. The above-mentioned structure can alsomaintain the battery capacity of the bare cell 100 and compactly couplesthe bare cell 100 and the protection circuit module 200, therebyincreasing the capacity density (battery capacity/volume) of thesecondary battery 10.

A conductive metal is patterned in the printed circuit board 210, and iselectrically connected to the PTC section 220, the protection circuitdevice 230, the charge/discharge terminal section 240, and the firstlead plate 250.

In one embodiment, the printed circuit board 210 is a flexible printedcircuit board. The thickness of the flexible printed circuit board 210is between about 0.1 and about 0.15 mm. The thickness of the flexibleprinted circuit board 210 is relatively thin as compared with aprotection circuit module used in an existing secondary battery. Assuch, in an embodiment of the present invention, the size of thesecondary battery is reduced, and the capacity density of the secondarybattery is increased. The sides of the printed circuit board 210 includea first short edge 211, a second short edge 212, a first long edge 213,and a second long edge 214. In one embodiment, an insulation tapeinsulating the printed circuit board 210 and the cap plate 131 isfurther provided between the printed circuit board 210 and the bare cell100. A bonding material is coated on opposite surfaces of the insulationtape to bond the printed circuit board 210 to the cap plate 131. Also,in one embodiment, exterior materials of the printed circuit board orflexible printed circuit board 210 include insulating materials and theconductive metal is patterned in the exterior materials. As such,insulation is maintained although the printed circuit board or flexibleprinted circuit board 210 is directly contacted with cap plate. That is,in one embodiment, the flexible printed circuit board 210 includes aninsulating portion (or a portion of the exterior materials that isinsulating) on a surface thereof facing the cap plate 131 to insulatethe conductive metal from the cap plate 131. The PTC section 220 islocated on the upper surface of the printed circuit board 210. Moreparticularly, the PTC section 220 includes a first tab 221 electricallyconnected to the terminal portion 215 formed on the upper surface of theprinted circuit board 210, and a PTC device 222 located on the first tab221 and electrically connected to the first tab 221, and a second tab223 located on the PTC device 222 and electrically connected to theelectrode terminal 134 protruding through the terminal hole 210 a. Thesecond tab 223 is welded to the electrode terminal 134 to be firmlycoupled to the electrode terminal 134, for example, by using laserwelding or resistance welding. The PTC device 222 is a device whoseelectric resistance reaches almost infinity if the temperature exceeds acritical value, and interrupts charge/discharge current when thetemperature of the secondary battery 10 is abnormally high. The PTCdevice 222 performs a reversible operation, such that the flow of thecurrent is stopped when the PTC device 222 is operated. Then, when thetemperature of the secondary battery 10 lowers, the resistance of thePTC device 222 decreases to thereby operate the secondary battery 10again. The PTC section 220 is electrically connected to the electrodeterminal 134 of the bare cell 100, and performs the function of (or ispart of) a negative electrode lead plate.

The protection circuit device 230 is formed on the printed circuit board210 at a distance away from the terminal section 215 with the terminalhole 210 a of the printed circuit board 210 therebetween. The protectioncircuit device 230 is made of a plurality of passive and active devicesand is electrically connected to the conductive metal patterned in theprinted circuit board 210. The protection circuit device 230 checksinformation about the charge/discharge state of the battery, and thecurrent, voltage, and temperature of the battery and protects thebattery.

The charge/discharge terminal section 240 is spaced apart from the upperend of the protective circuit device 230 by a distance, and is mountedto the surface of the printed circuit board 210. The charge/dischargeterminal section 240 is electrically connected to a conductive metal onthe printed circuit broad 210 to function as an electrical path to anexternal electronic device. The charge/discharge terminal section 240will be described in more detail later with reference to FIGS. 6 to 8.

The first lead plate 250 is located at (or at a portion of) the firstshort edge 211 of the printed circuit board 210 and is electricallyconnected to the cap plate 131. Accordingly, the first lead plate 250 isa positive electrode lead plate. More particularly, the first lead plate250 includes a first plate 251 electrically connected to the first shortedge 211 of the printed circuit board 210 and having a flat shape, asecond plate 252 electrically connected to the cap plate 131 and havinga flat shape, and a third plate 253 electrically connecting the firstplate 251 and the second plate 252. The first plate 251 is soldered tothe printed circuit board 210. The second plate 252 and the cap plate131 are firmly connected to each other, for example, by laser welding.The height of the third plate 253 has a height separating the firstplate 251 from the second plate 252. In addition, the printed circuitboard 210 has a thickness substantially identical to a sum of the heightseparating the first plate 251 from the second plate 252 and a thicknessof the second plate.

An existing lead plate defines an extra space between a bare cell and aprotection circuit module spaced apart from the bare cell and connectsthe bare cell to the protection circuit module. Accordingly, the leadplate has a height corresponding to the extra space, thereby leaving anunnecessary space after the secondary battery is manufactured. However,in the secondary battery 10 according to an embodiment of the presentinvention, the protection circuit module 200 makes surface-contact withthe upper surface of the cap plate 131, and the first plate 251 islocated on the upper surface of the protection circuit module 200. Dueto the above-mentioned structure, the height of the third plate 253 issubstantially similar to the thickness of the printed circuit board 210,and the first lead plate 250 connects the bare cell 100 and theprotection circuit module 200. Accordingly, the extra space forconnecting the cap plate 131 and the first lead plate 250 is removed,thereby enabling manufacturing of a compact secondary battery 10 andreducing the overall size of the secondary battery 10. In addition, thebattery capacity of the bare cell 100 is maintained and the bare cell100 and the protection circuit module 200 are compactly coupled to eachother, thereby increasing the capacity density (battery capacity/volumeof the secondary battery) of the secondary battery 10.

The second lead plate 260 is located at (or at a portion of) the secondshort edge 212 of the printed circuit board 210 and is connected to thecap plate 131. The second lead plate 260 is electrically connected tothe cap plate 131 and functions as a positive electrode lead plate likethe first lead plate 250. However, the second lead plate 260 may be adummy plate having a structure corresponding in shape to the first leadplate 250. When the second lead plate 260 is a dummy lead plate, thesecond lead plate 260 mechanically connects the bare cell 100 and theprotection circuit module 200, thereby improving coupling force. In oneembodiment, the second lead plate 260 has the same (or substantially thesame) structure as the first lead plate 250 regardless of the fact thatthe second lead plate 260 is a positive lead plate or a dummy plate.

The second lead plate 260 may be removed from the secondary battery 10.An existing second lead plate defines an extra space between a bare celland a protection circuit module. However, in the secondary battery 10according to an embodiment of the present invention, there is no extraspace between the protection circuit module 200 and the secondarybattery 10. Accordingly, when the second lead plate 260 is a dummyplate, the structure of the secondary battery 10 is made simple byremoving the need for an actual lead plate for electrical connectionfrom the secondary battery 10, and the structure of the dummy plate alsoreduces the overall size of the secondary battery 10. In addition, themanufacturing cost of the secondary battery 10 is reduced and themanufacturing process thereof is simplified by removing the need for anactual lead plate for electrical connection.

FIG. 6 is a schematic exploded perspective view of the charge/dischargeterminal section 240 according to an embodiment of the presentinvention. FIG. 7 is a schematic perspective view of thecharge/discharge terminal section 240 according to an embodiment of thepresent invention. FIG. 8 is a schematic perspective view of thesecondary battery 10 according to an embodiment of the presentinvention.

Referring to FIGS. 6 to 8 together with FIGS. 1 and 3, thecharge/discharge terminal section 240 according to an embodiment of thepresent invention is located on the printed circuit board 210 and theprotection circuit device 230. The charge/discharge terminal section 240can be divided into a housing 241 and a charge/discharge terminal 242according to their materials. The charge/discharge terminal section 240can also be divided into a base 243, a first support 244 and a secondsupport 245 according to their structures. The charge/discharge terminalsection 240 is exposed by a charge/discharge terminal opening 620 a ofthe upper case 620.

Referring to FIG. 6, the housing 241 and the charge/discharge terminal242 of the charge/discharge terminal section 240 may be integrallyformed. In FIG. 6, it should be understood that the housing 241 and thecharge/discharge terminal 242 are separated for purposes of convenience.The housing 241 has a groove having a set (or predetermined) width and aset (or predetermined) length at a central portion of the lower surfacethereof, and the cross-section taken along the short edge issubstantially U-shaped. The housing 241 is made of an insulationmaterial. The charge/discharge terminal 242 has three metal plates thatfunction as a positive electrode, a resistor, and a negative electroderespectively. More particularly, the charge/discharge terminal is madeby plating phosphor bronze with gold. A lower portion of thecharge/discharge terminal 242 is mounted to a surface of a mount portion217 located on the sides of the first long edge 213 and the second longedge 214 of the printed circuit board 210. The charge/discharge terminal242 is electrically connected to a conductive metal of the printedcircuit board 210.

Referring to FIG. 7, the charge/discharge terminal section 240 includesa base 243 having a flat plate-like shape, and a first support 244 and asecond support 245 supporting opposite sides (or opposite side portions)of the base 243. In this case, it should be understood that the housing241 and the charge/discharge terminal 242 are coupled to each other. Thefirst support 244 and the second support 245 are located on a portion ofthe first long edge 213 and a portion of the second long edge 214 of theprinted circuit board 210 to support the base 243.

Referring to FIG. 8, the base 243 of the charge/discharge terminalsection 240 is located on the protection circuit device 230, and thefirst support 244 and the second support 245 are located on the firstlong edge 213 and the second long edge 214 of the printed circuit board210, respectively. More particularly, the protection circuit device 230is located between the first support 244 and the second support 245, andthe lower surface of the base 243 is supported by the first support 244and the second support 245 such that it is spaced apart from theprotection circuit device 230.

The charge/discharge terminal section 240 having the above-mentionedstructure only needs a small area to be mounted to the printed circuitboard 210, and is located on the protection circuit device 230 such thatit is formed to be compact on the printed circuit board 210.Accordingly, all devices necessary for manufacturing of the protectioncircuit module 230 can be efficiently disposed on one surface of theprinted circuit board 210. As a result, the secondary battery 10 can bemade to be relatively small and the capacity density (batterycapacity/volume) of the secondary battery can be increased.

FIG. 9 is a schematic side view of a first lead plate 250 a according toanother embodiment of the present invention. FIG. 10 is a schematic sideview of a first lead plate 250 b according to yet another embodiment ofthe present invention.

Referring to FIG. 9, the first lead plate 250 a includes a first plate251 a and a second plate 252 a. The first plate 251 a is electricallyconnected to the first short edge of the printed circuit board and has aflat shape. The second plate 252 a is electrically connected to the capplate and has a flat shape. The first plate 251 a and the second plate252 a are connected with each other mechanically and electrically. Thefirst plate 251 a is soldered to the printed circuit board, and thesecond plate 252 a is connected to the cap plate through the welding.

Referring to FIG. 10, the first lead plate 250 b has a flat shape. Whenthe printed circuit board is a flexible printed circuit board, athickness of the flexible printed circuit board is between about 0.1 andabout 0.15 mm. In fact, when the first lead plate 250 b is connected tothe flexible printed circuit board, there can be some step or leveldifference due to thickness of the flexible printed circuit board. Butbecause the thickness of the flexible printed circuit board is muchthinner than an existing rigid printed circuit board, the first leadplate 250 b can be connected to the cap plate without a substantiallevel difference (i.e., be connected substantially flush or flat withthe cap plate).

As mentioned above, the secondary battery 10 of FIGS. 1 to 10 disclosesa thin protection circuit module 200 and a coupling relation between thebare cell 100 and the protection circuit module 200.

The secondary battery 10 according to an embodiment of the presentinvention has structure in which all of the PTC section 220, theprotection circuit device 230, the charge/discharge terminal section240, and the lead plates 250 and 260 couple electrically andmechanically to one surface of the printed circuit board 210.Accordingly, the secondary battery 10 can be made to be relative thin orslim by removing an extra space between the existing bare cell and theexisting protection circuit module. Further, there is no redundant andseparate space that is needed in the secondary battery 10 due to compactarrangement of devices. Furthermore, the thin printed circuit board 210is employed as the protection circuit board of the secondary battery 10,thereby reducing the thickness caused by a separate substrate.

Accordingly, the above-mentioned secondary battery 10 reduces the sizesof internal devices and compactly locates the internal devices, therebyreducing the size of the secondary battery 10. In other words, thecapacity density (battery capacity/volume) of the secondary battery 10can be increased by compactly coupling the bare cell 100 and theprotection circuit module 200 while maintaining the battery capacity ofthe bare cell 100.

That is, in view of the foregoing, a secondary battery according to anembodiment of the present invention includes a core pack having a barecell and a protection circuit module. Typically, there are some spacesbetween the protection circuit module and the bare cell. Theseunnecessary spaces increase the overall size of the secondary batterywithout increasing its power density.

By contrast, a secondary battery according to an embodiment of thepresent invention includes a protection circuit module formed with aprinted circuit board that makes surface-contact with an upper surfaceof the bare cell so that an unnecessary space between the bare cell andthe protection circuit module can be removed to thereby reduce theoverall size of the secondary battery and/or to increase the powerdensity of the secondary battery.

In one embodiment, the printed circuit board is a flexible printedcircuit board. In addition, the secondary battery may further include acharge/discharge section that is mounted to the printed circuit boardutilizing a surface mounting technology. Also, the secondary battery mayinclude a lead plate having a step structure for connecting the barecell to the flexible circuit board without any space therebetween.

While the invention has been described in connection with certainexemplary embodiments, it is to be understood by those skilled in theart that the invention is not limited to the disclosed embodiments, but,on the contrary, is intended to cover various modifications includedwithin the spirit and scope of the appended claims and equivalentsthereof.

What is claimed is:
 1. A secondary battery comprising: a bare cell; anda protection circuit module on the bare cell and comprising a lead plateat a short edge portion of the protection circuit module and a printedcircuit board surface contacting a cap plate, the lead plate being onboth the bare cell and the printed circuit board.
 2. The secondarybattery of claim 1, wherein the printed circuit board is a flexibleprinted circuit board.
 3. The secondary battery of claim 2, wherein theflexible printed circuit board comprises an insulating portion on asurface thereof facing the cap plate.
 4. The secondary battery of claim1, wherein the protection circuit module comprises a charge/dischargeterminal section on the printed circuit board and for electricallyconnecting the bare cell to an external device.
 5. The secondary batteryof claim 4, wherein: the charge/discharge terminal section comprises ahousing and a charge/discharge terminal on the housing, and thecharge/discharge terminal section is surface mounted to the printedcircuit board.
 6. The secondary battery of claim 5, wherein thecharge/discharge terminal is comprised of a plurality of metal plates,the plurality of metal plates comprises a positive electrode, anidentification resistor and a negative electrode insulated from eachother by the housing.
 7. The secondary battery of claim 4, wherein thecharge/discharge terminal section comprises: a base having a flatplate-like shape; a first support mounted on the printed circuit boardand for supporting a first side portion of the base to be spaced apartfrom the printed circuit board; and a second support mounted on theprinted circuit board and for supporting a second side portion of thebase to be spaced apart from the printed circuit board.
 8. The secondarybattery of claim 7, further comprising a protection circuit device onthe printed circuit board and between the first support and the secondsupport, wherein a side of the base facing the protection circuit deviceis supported by the first and second supports to be spaced apart fromthe protection circuit device.
 9. The secondary battery of claim 1,wherein the printed circuit board has a thickness between about 0.10 toabout 0.15 mm.
 10. The secondary battery of claim 1, wherein the printedcircuit board has smaller area than that of the cap plate.
 11. Thesecond battery of claim 1, wherein the printed circuit board contactsthe bare cell without any device between the printed circuit board andthe bare cell.
 12. The secondary battery of claim 1, further comprisinga positive temperature coefficient (PTC) section on the printed circuitboard, wherein: the printed circuit board has a terminal hole; and thebare cell comprises an electrode terminal electrically connected withthe positive temperature coefficient (PTC) section through the terminalhole.
 13. The secondary battery of claim 12, wherein the electrodeterminal extends into a first end of the terminal hole facing the barecell and out from a second end of the terminal hole facing away from thebare cell.
 14. The secondary battery of claim 12, wherein the printedcircuit board is a flexible printed circuit board and wherein the PTCsection comprises: a first tap electrically connected with a terminal ona side of the flexible printed circuit board facing away from the barecell; a second tap electrically connected with the bare cell; and a PTCdevice electrically connected with the first tap and the second tap. 15.The secondary battery of claim 12, wherein the PTC section is at least aportion of a positive or negative lead plate.
 16. The secondary batteryof claim 1, wherein the lead plate being electrically connected withboth the bare cell and the printed circuit board.
 17. The secondarybattery of claim 1, wherein the lead plate comprises: a first plate onand mechanically and electrically connected with the printed circuitboard at the short edge portion of the printed circuit board; a secondplate on and mechanically and electrically connected with the bare cell;and a third plate electrically connecting the first plate and the secondplate and having a height separating the first plate from the secondplate, and wherein the printed circuit board has a thicknesssubstantially identical to a sum of the height separating the firstplate from the second plate and a thickness of the second plate.
 18. Thesecondary battery of claim 1, wherein the lead plate is a substantiallyflat plate.
 19. The secondary battery of claim 1, further comprising adummy plate at another short edge portion of the printed circuit boardfor mechanically connecting the bare cell with the protection circuitmodule.
 20. The secondary battery of claim 1, further comprising anotherlead plate at another short edge portion of the printed circuit boardand electrically connected with the bare cell, the two lead plates beingintegrated as at least a portion of a positive or negative lead plate.